Locomotive train cars are required to have handbrake systems. State-of-the-art freight car handbrakes are manpower intensive. Setting and releasing handbrakes exposes operators to safety hazards, and the potential for human error exposes train operations to the potential for time delays, maintenance issues, and ultimately, the potential for rail accidents. Regulations provide that a train may not hold itself on a grade by using the air brakes alone. When the grade becomes too steep for the locomotive handbrakes to hold the train, a crewmember is required to leave the locomotive to set the handbrakes on several of the freight cars. This may be a significant inconvenience to the train crew during times of repeated stoppages on non-horizontal terrain, and it can add to overall operations time.
Problems associated with handbrakes include (1) moving a train with set handbrakes and (2) inadequately setting the brakes when parking a train. Set handbrakes on a moving train can be the result of operator error or negligence. For instance, when a train is to be stopped for an extended period, a trainman must walk to set the handbrakes on a sufficient number of cars to securely park the train. The trainman must walk this distance again and release the brakes when the train is to be moved. A common practice is to set just enough handbrakes to maintain a train""s position under given circumstances. With changes in terrain and weather, the actual number of brake settings may vary. A different trainman may release the handbrakes and since it is difficult to visually discern a set handbrake from a released handbrake, some handbrakes may be left in the set position. These factors can result in a train being moved with one or more handbrakes set.
If a train is moved while a handbrake is set, the wheels on an empty car may not turn when the train begins to move, resulting in flattening of the wheels. Wheels damaged in this way must be replaced, which requires the car to be taken out of service and brought to a suitable repair facility, at significant expense and schedule impact. Wheels on a heavily loaded freight car may not skid due to the traction resulting from the greater contact force on the rail. However, an inadvertently set handbrake can damage the running gear due to overheating and rapid brake wear. Studies have shown that xe2x80x9chandbrake left on,xe2x80x9d and flat wheel spots, often caused by moving a train with a set handbrake, are common causes of train failures.
Improper setting of handbrakes is another problem. Proper handbrake application requires a force of 125 lbs. at the handwheel and this force may be missed by weak or inexperienced operators because there is no tangible feedback to the handbrake operatorxe2x80x94they must rely on xe2x80x9cfeel.xe2x80x9d When handbrakes are set with inadequate force, a car can roll down a slight grade or be blown along the tracks by high winds, causing accidents.
The handbrake actuator system of the present invention overcomes the problems of the prior art. It can be installed on any of a train""s freight cars in the region currently occupied by the handwheel, and it can be connected to the existing brake chain. The system can be designed for automated operation and monitoring of each car from the Head End Unit (HEU), which can be located in the locomotive and operated by the engineer. Manual operation is also enabled by either a pneumatic lever or by a hand crank (requiring significantly less force than 125 lbs. for operation) at car-side. If desired, the set condition of the brake can be immediately identifiable when viewing the car from a distance.
According to one aspect of the invention, the actuator consists of a compression coil spring/piston arranged to apply tension to the handbrake chain. The default condition is the xe2x80x9csetxe2x80x9d position. Two redundant systems may be provided to release the brake. The first is an air actuator connected in series with the spring and chain. Applying air pressure (remotely or by local levers) compresses the spring and releases the handbrake. Secondly, a manual handwheel type actuated mechanism will also compress the spring and release the brake.
In the Electronically Controlled Pneumatics (ECP) system in modern trains, each rail car currently has access to a 230 volt DC (VDC) line of which 10 watts of power are available to each car. The present invention can take advantage of this power availability for reliable function, operation and monitoring. Moreover, the present invention can be arranged to interface with the existing Car Control Device (CCD) (a component of the ECP system) currently used in the art. Thus, the present invention may be readily integrated into state-of-the-art freight cars.
In modern trains, a single brake pipe containing 90 psi air pressure (as measured near the compressor, 75 psi at the train""s far end) with a minimum delivery capability of 60 cubic fee per minute (cfm) is used to charge the primary brake system of each car. The present invention can be arranged to utilize this pre-existing supply of air, if desired. Additionally, existing air brake systems have an air reservoir on each freight car. The handbrake system of the invention can be arranged so as not to interfere with the existing air brake systems.
The present invention can be used to provide a reliable, constant force to the friction mechanism at the wheels. Freight cars typically have a chain that connects the existing force-producing mechanism to the friction mechanism. The present invention may be integrated to use this brake chain. Currently, brake systems are tested to ensure the tension on the brake chain is between 3350 and 6200 lbs. when a force of 125 lbs. is applied to a handwheel (for conventional vertical wheel handbrakes). It would be highly desirable to reduce this handwheel force requirement for setting the brakes. In addition, operation from the side of the car without the requirement to mount the car to operate the brake is highly desirable. The location of the handwheel in the prior art requires operators to place themselves between cars to operate it, and often involves climbing onto the car itself.
An object of the present invention is to provide a brake system that is rugged enough to work reliably in the typical freight car environment, taking into account shock, intense vibration, severe temperature changes, moisture, etc. If desired, the present invention can be uncomplicated and compact enough to fit within a similar space envelope to that of prior art handwheel type handbrake system. It would be advantageous for a new system to bolt directly as is, or with some modification, into the space currently occupied by the handwheel-type handbrake so that the system can accommodate the hand mechanisms at the sides of the car.
The above and other characteristics and advantages of the handbrake system of the invention can be better understood from an analysis of the following written description and the accompanying drawings, where like reference numbers represent like elements.